When Apple updated its iBooks e-book application to 1.5, they included some nice new fonts: Ahtelas, Charter, Iowan, and Servavek. With a little work, you can extract these from the application and use them on your Mac.

The STIX fonts are only for mathematical and technical symbols used by Elsevier journals, that Apple has included in the app.

From the font note:

Arie de Ruiter, who in 1995 was Head of Information Technology Development at Elsevier Science, made a proposal to the STI Pub group, an informal group of publishers consisting of representatives from the American Chemical Society (ACS), American Institute of Physics (AIP), American Mathematical Society (AMS), American Physical Society (APS), Elsevier, and Institute of Electrical and Electronics Engineers (IEEE). De Ruiter encouraged the members to consider development of a series of Web fonts, which he proposed should be called the Scientific and Technical Information eXchange, or STIX, Fonts. All STI Pub member organizations enthusiastically endorsed this proposal, and the STI Pub group agreed to embark on what has become a twelve-year project. The goal of the project was to identify all alphabetic, symbolic, and other special characters used in any facet of scientific publishing and to create a set of Unicode-based fonts that would be distributed free to every scientist, student, and other interested party worldwide. The fonts would be consistent with the emerging Unicode standard, and would permit universal representation of every character. With the release of the STIX fonts, de Ruiter's vision has been realized.

Un-zipping the .ipa app file opens up access to sounds and graphics as well. Lots of possibilities for alert sounds on phones and computers. Be mindful of copyright restrictions before considering re-distribution of content.

I'm glad to see Apple including STIX fonts with iBooks. As someone has noted, they're a standard, freely distributed set of math and scientific fonts. It'd be great if Apple would add them to OS X. Before I discovered STIX, I spent a heck of a lot of time coming up with fonts for a science book I was editing.